A direct current circuit breaker is difficult to achieve interruption or cutting-off performance because there is no zero point in the current to be cut off unlike an alternating current circuit breaker.
An air type circuit breaker is arranged to interrupt an arc stretched in an arc chute. Therefore, the air circuit breaker might become unable to confine the current and cause ground fault.
A vacuum type circuit breaker is arranged, as shown in a dc high speed vacuum circuit breaker (HSVCB) disclosed in Non-patent Documents 1 and 2, for example, to produce a zero current point forcibly by injecting current in a direction opposite to a main circuit current in a vacuum valve, and thereby interrupt the current.